The purpose of this study is to study the nature of cells in immediate and late phase reactions to oral food challenges and look for presence of delayed- onset reactions to foods. Hypotheses: 1. Mediators released in the serum will reflect activation of mast cells and eosinophils after, respectively, immediate and late phase reactions to oral food challenge. 2. In a negative immediate challenge, symptom scores will show no difference between placebo and active weeks during prolonged double-blind feeding of suspected foods.